Polypropylene has been widely used as a thermoplastic molding material with superior rigidity, heat resistance, transparency, and the like. However, this polypropylene lacks flexibility, and when used as an adhesive, a soft rubber component is usually blended to the polypropylene. Even though a polypropylene-based adhesive with an improved adhesion property is thus obtained by blending a soft rubber component to the polypropylene (see, for example, Patent Documents 1 and 2), there has been, on the other hand, a problem that adhesive strength of the adhesive deteriorates when subjected to a heat history at a temperature of 40° C. or higher. Thus, advent of a polypropylene-based adhesive excellent in both initial adhesion and adhesion after a heat history has been desired.
Patent Document 1: Japanese Patent Laid-Open Publication No. H9-111069
Patent Document 2: Japanese Patent Laid-Open Publication No. H4-300933